Chapter 12. Direct Measurement of Tension in the Intact Heart: Diastolic Volume-Systolic Pressure-Tension Relation

  1. Ruth Porter and
  2. David W. Fitzsimons
  1. B. Lewartowski,
  2. J. Michaeowski and
  3. G. Sgdek

Published Online: 30 MAY 2008

DOI: 10.1002/9780470720066.ch12

Ciba Foundation Symposium 24 - Physiological Basis of Starling's Law of the Heart

Ciba Foundation Symposium 24 - Physiological Basis of Starling's Law of the Heart

How to Cite

Lewartowski, B., Michaeowski, J. and Sgdek, G. (1974) Direct Measurement of Tension in the Intact Heart: Diastolic Volume-Systolic Pressure-Tension Relation, in Ciba Foundation Symposium 24 - Physiological Basis of Starling's Law of the Heart (eds R. Porter and D. W. Fitzsimons), John Wiley & Sons, Ltd, Chichester, UK. doi: 10.1002/9780470720066.ch12

Author Information

  1. Department of Clinical Physiology, Medical Centre of Postgraduate Education, Warsaw

Publication History

  1. Published Online: 30 MAY 2008
  2. Published Print: 1 JAN 1974

ISBN Information

Print ISBN: 9789021940250

Online ISBN: 9780470720066

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Keywords:

  • ventricular performance;
  • aortic pressure;
  • electromagnetic flow meter;
  • ventricular walls;
  • peristaltic pump

Summary

The mechanical consequences of the changing left ventricular geometry which attends the Starling-type regulation of ventricular performance have been investigated in isolated dog hearts and those in situ. The measurements of aortic pressure and left ventricular systolic and diastolic pressure were made by means of cardiac catheterization and electromanometers, of aortic flow with an electromagnetic flow meter and of circular wall tension (T) with a strain-gauge transducer whose points of coupling were brought closer together after it had been fixed in placz. The volume was changed by injecting known amounts of blood into the emptied, closed left ventricle of the isolated hearts perfused with blood. Diastolic pressure in the hearts in situ was changed by exsanguination and blood transfusion. Totally isovolumic left ventricular beats were produced in the hearts in situ by clamping the ascending aorta. Plots of maximal tension (T0) developed during the isovolumic beats, of stroke volume and of stroke work against left ventricular end-diastolic pressure show no descending limb for these three parameters up to pressures as high as 47 g/cm2, although a marked, protracted descending limb in the plot of maximal isovolumic pressure (P0) was observed. Plots of systolic pressure (P) against the tension, T, measured every 20 ms during the single isovolumic beats, show that, at low and medium left ventricular end-diastolic pressures and volumes, P is a linear function of T, whereas at higher values increasing deviations from linearity were observed. The T/P ratio increased with increasing diastolic volumes with a resulting increase of afterload at an estimated diastolic aortic pressure of 100 g/cm2. However, the ratio T0/T was greater than 1.6 at the highest diastolic pressures obtained (47 g/cm2). This helps to explain why we observed no descending limb in the plots of stroke volume and stroke work. Our results fit well with predictions based on an ellipsoidal reference model (except for the deviations from linearity) and help us to evaluate the mechanical and haemo-dynamic consequences of changing ventricular diastolic geometry.